The present invention relates to a topsheet used for body fluid absorptive articles such as sanitary napkins and disposable diapers and also to a method for making the topsheet.
It is well known to form a topsheet used for body fluid absoptive articles, to provide this sheet with a plurality of liquid passages each extending through the sheet from an upper opening to a lower opening so that the upper surface comes in contact with a wearer's skin, and the lower openings of the liquid passages are in contact with a liquid-absorbent core, and thus body fluids are introduced into the liquid-absorbent core under a capillary action occurring within the respective liquid passages.
For example, Japanese Patent Publication No. 1982-17081 discloses a technique such that a topsheet made of polyethylene sheet is provided with liquid passages each in the form of truncated cone-shaped capillary tube and a lower end of each liquid passage is arranged in close contact with a liquid-absorbent core.
Japanese patent application Disclosure No. 1995-58950 discloses a technique Such that thermoplastic synthetic fibres are melt-blown to form nonwoven fabric which is then formed with liquid passages and fibrous fluff is formed around lower openings of the liquid passages to obtain a topsheet.
In both of the above-mentioned prior techniques, the lower end of each liquid passage should be always in close contact with the liquid-absorbent core. However, the topsheet which is thin and less rigid is readily wrinkled during the practical use of the body fluid absorptive articles and, in consequence, the lower end of each liquid passage is separated from the liquid-absorbent core, preventing the body fluids from being smoothly transferred into the liquid-absorbent core.
Generally, the soft touch is indispensable to the body fluid absorptive articles. For example, in the case of the liquid-absorbent core formed of fluff pulp, a density thereof is limited, since an excessively high density of the fluff pulp would give a wearer the unpleasant stiff touch. However, an excessively low density of the fluff pulp would reduce the diffusibility of the body fluids. As a result, the body fluids transferring from the liquid passages to the liquid-absorbent core can not rapidly diffuse laterally from the lower openings and the body fluids stay on the topsheet for a correspondingly longer time, giving a wearer the discomfortable feel of wetness.
Accordingly, it is a principal object of the invention to solve the problem encountered by the previously mentioned prior techniques by composing a topsheet from a first sheet and a second sheet, bonding the second sheet to the first sheet around lower openings of respective liquid passages formed through the first sheet and adjusting a density of the second sheet at a level of a density of a liquid-absorbent core.